im new to this site and have looked but im not sure what the problem could be. i have a 97 f-150 4x4 with the 4.6 and 4r70w trans. sometimes when i drive for more than 15 min or so the truck starts to buck in overdrive and even keeps doing it when im slowing down but once it shifts out of od its fine till it goes back in. it does it on and off the throttle. my overdrive button and light do not work so i have no clue if its flashing. any help would be appreciated.

 

I'll stab at it.


Common problem: "Low grade misfire", it really annoys a lot of people and can be difficult to remedy. Have you changed plugs lately? (Motorcraft or go home in some peoples eyes, I prefer NGK, others like Denso.) If you have, or plan to soon make sure you use dielectic grease/compound in the boots.

Less common problem: problems with the rear axle. After I've gotten my 3/4 ton axle (sterlin 10.5) under the rear, I took it for a spin and the back of the truck does not jump up and down like the 8.8 did. I believe I have tweaked my axle.


I dont think I've changed the light bulb, but cant fathom it being too difficult to get to.


You could have the dealer scan for trans codes, autozone/napa/schucks dont have a scanner for trans. A trans shop should though too.

 

thanks for the info. i was thinking it was the misfire but no one else seemed to have the problem the whole time in overdrive weather on the gas hard light or not at all and on the brakes. and its not all the time either only pretty much when it feels like it. the plugs were changed not too long ago with ngk's. and as for the rear axle it does feel like theres some slop when starting out from a stop but it has always felt like that. i was also thinking maby it is from the torque converter lock out but its not like a shutter, its more like the truck is dieing and starting back up every few seconds. it bucks pretty good sometimes and sometimes its light. and theres no tach to watch the rpms.

 

Ok, now if your getting the same jumping feeling while on the brakes/coasting, I would be more prone to look elsewhere than the motor/trans. But even now from what youve said it sounds like you have a misfire (dielectic compound is strongly encouraged.)


Also can you verify your check engine light comes on when you start the truck? I bought mine and did not notice for two years the light was removed, covering up a CEL. I'd have to see the truck in person to have a better idea, because to me, dying intermittently is very different than a misfire, which would usually throw a code and probably get my attention toward cam or crank position sensor.


Back to bouncy bouncy, I had issues that would never go away, but tire pressure and fresh tie-rods did seem to make a minor impact as well as bolting the idler arm back to the frame. Make sure things are in good shape up front also.

The oddest thing about my plagued bounce is that it always felt like some fat kid was jumping in my truck bed. hell the bed bounced visibly so it even looked like it.

 

the light works and is not on. i have no idea what is going on. im gonna take it to the ford garage monday and see what they can come up with. thanks a bunch for the help!

 

I'm wondering if this isn't an ignition problem that could be (relatively) easy to fix: either in the coils, the plug wires, or both.

How many miles on those coils and on the wires themselves? What do the wires look like? I would CERTAINLY take a good look at this before you go to the dealer. A weak coil or weak wires would cause a misfire, especially under load like acceleraation in overdrive, and weak wires could be causing a crossfire situation.

Just my $0.02.

 

im not sure when the last time they were changed was. the truck has 140k on it. the wires look kind of old but in good shape. i was just gonna have the dealer hook it up to a scanner and see what they could find if anything since the check engine light isnt on. ill try replacing the coils and wires and plugs and see what happens. thanks a bunch!

 

This is a long shot, but the Idle Air Control valve could cause a condition as described.

 

if it was the iac valve wouldnt the check engine light come on?

 

Nope, most often the light doesn't come on.

Darrin

 

i had same issue, come to find out a plug wire got caught in the fan. cost me 120 bucks to find that out. You check engine light should flash on a misfire, and depending on nuber of flashes, it tells you witch cylinder.